Ah, the American dollar. Speaking ill of it, will, in some circles, earn you a sterner response than outright blasphemy against Jesus. Or maybe it's because the banks arguably own the government . Americans are sensitive about their currency, which should be yet another obvious revelation to anyone paying attention to the ennui gripping the US as the federal deficit climbs to ever-greater levels . The observation arose not while studying a macroeconomic treatise, but while sorting out a pile of coins: I'm taking a short trip to the US today and after my last adventure in March, I'm taking a lesson to heart: you don't mess with their money. In Canada we treat coins from Canada or the US at par. The 10-20% difference in currencies is so minor, in Canada only the greatest scold would care where your penny, dime or nickel came from. The line is often drawn at quarters, as vending machines usually reject the foreign coin, but up to ten cents, it's generally fair game. Not...